In 1987, Tang, C. W. et al. (Appl. Phys. Lett., 51, 913 (1987)) reported an organic light-emitting diodes having a structure of ITO/Diamine/AlQ3/Mg:Ag by evaporation of organics and metals, wherein ITO is a transparent conductive indium/tin oxide as anode, diamine as hole transport material, AlQ3 is tris(8-hydroxyquinoline) aluminum as both electron transport and emissive material. This device has an external quantum efficiency of 1% and brightness of 1000 cd/m2 at 10 V, which motivates a rapid development in the research of organic light emitting diodes. In 1990, Friend, R. H. et al. from the Carvendish laboratory in England made a polymer light emitting diode with a structure of ITO/PPV/Al, wherein PPV is a conjugated polymer, poly(p-phenylene vinylene). This device gives an external quantum efficiency of 0.05% and emits yellowish green light (Nature, 347, 539 (1990)). It indicates the beginning of solution processable polymer light emitting diodes. These devices utilize only the singlet exciton, wherein the rest exciton in total ¾ as the triplet is not utilized. In 1998, Forrest, S. R. et al. made a high efficiency electrophosphorescent organic light emitting diode by using platinum organic complex (Nature, 395, 151 (1998)). The triplet state of Pt complex has short lifetime and thus partial singlet property because of the spin-orbit coupling. The iridium organic complex has even stronger spin-orbit coupling and can emit various phosphorescent colors of light with different ligands [Lamansky, S. et al., J. Am. Chem. Soc., 123, 4304 (2001); Inorg. Chem., 40, 1704 (2001)]. High efficiency electrophosphosecent organic light emitting diodes emitting red, yellow, green, blue and white light were carried out [Baldo, M. A., et al., Appl. Phys. Lett., 75, 4 (1999). Adachi, C., et Al., Appl. Phys. Lett., 77, 904 (2000). Adachi, C., et al., Appl. Phys. Lett., 78, 1622 (2001). Adachi, C., et al., Appl. Phys. Lett., 79, 2082 (2001). D'Andrade, B. W., et al., Adv. Mater., 14, 147(2002)]. These small organic complexes were also blended with polymers and used for polymer light emitting diodes [Lee, C., et al., Appl. Phys. Lett., 77, 2280 (2000). Zhu, W., et al., Appl. Phys. Lett. 80, 2045 (2002]. Chen, F., et al., Appl. Phys. Lett., 80, 2308 (2002)]. However, these blend systems always have phase separation problem and higher operation voltages since large amount of small molecular charge transport materials were added. The researchers in our laboratory have introduced charge transport moieties into PPV via covalence bond to get balance of charge injection and transport, and solve the phase separation problem in physically blend system and simultaneously simplify the device fabrication process (no need for additional electron transport layer) [Lee, Y. et. al, J. Am. Chem. Soc., 123, 2296 (2001). U.S. Pat. No. 6,495,644 (2002)]. Thus it is highly desirable to develop electroluminescent materials without phase segregation problem, which can both utilize the high efficiency of phosphorescent metal-organic complexes and carry charge transport moiety for balancing the charge transport and injection.